As is known, power take-offs are mechanical devices which take power from a motor in order to operate machine tools borne or trailed by a vehicle powered by the same motor.
The devices are applicable to motors of industrial vehicles or the transmission groups thereof, and are (in the case of being applied to motors) independent of the movement of the vehicle, and can be used, therefore, for applications when the vehicle is stationary. In both cases of application, the engagement of the power take-off is generally commanded by a hydraulic control acting on a multiple disc clutch comprised on the device.
When the power take-off is not in use, and the clutch is not activated, there is a level of noise which is caused by the intermediate and secondary gearings comprised in the device, which are rotated by the drive gearings. The cogs of the intermediate gearings tap continuously against the cogs of the second gearing and the primary gearing due to the necessary coupling between them, and as the driven gearings are free to move at variable angular velocities, oscillating at about the speed of the primary gearing connected to the vehicle motor.
Any reduction in the interaxes between the various gearings would certainly reduce, or even solve the problem, but such a reduction would also lead to gearing interference which, apart from generating a further though different sort of noise, would also give rise, during normal operation of the power take-off, to dangerous overloads of the cogging and equally dangerous loss of lubrication due to absence of oil circulation.
The main aim of the present invention is to provide a power take-off for industrial vehicles which is quiet, both during non-functional operation and when under load, while at the same time exhibiting characteristics of absolute efficiency and reliability.
A further aim of the invention is to provide a power take-off which exhibits innovative characteristics of quietness and reliability together with manufacturing costs that are contained with respect to the standard.
The above aims and more besides are all attained by the power take-off of the invention, in particular for industrial vehicles, of a type in which an intermediate gearing enmeshes with an external drive gearing, and a driven gearing can be constrained to the drive shaft of the power take-off, the power take-off being characterised in that it comprises gearings having conical directrices, the relative position of which is a function of the action exerted by elastic means acting in the direction of the rotation axis of at least one of the gearings and the torque transmission between the gearings.
The intermediate gearing is advantageously constituted by a pair of cylindrical cogwheels, one of which comprises a cylindrical cogging and is couplable with external drive gearings, while the other comprises a conical cogging and enmeshes with the driven gearing which is constrainable to the output shaft of the power take-off.
The position of the driven gearing with respect to the intermediate gearing is constrained by the action of the elastic means acting axially on the driven gearing; the entity of the action is such as to cause, during non-operative functioning of the power take-off, a relative positioning in which play between the cogs of the gearings is eliminated, while, when operating functionally, the positioning attained re-achieves the normal amount of play, preventing faulty interferences and guaranteeing correct hydraulic loads.
The advantages of the invention with respect to prior art power take-offs are obvious, as it removes the causes which cause high noise levels during non-operative functioning, and also correct functioning of the transmission when transmitting power to the machine tool connected to the output shaft thereof.